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Bulletin  278  May,  1926 


(Eatuwrtirut  Agrtntltitral  iExpmmrtti  -8>tatum     1     , 

•Dfatii  3Bau?tt,  (Hannutxmt 


A  Chemical  Investigation  of  Some 
Standard  Spray  Mixtures 


R.   E.   ANDREW  AND   PHILIP  GARMAN 


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CONNECTICUT  AGRICULTURAL    EXPERIMENT  STATION 


OFFICERS  AND  STAFF 

as  of 
May,  1926 


BOARD  OF  CONTROL 
His  Excellency,  John  H.  Trumbull,  ex-officio,  President. 

Charles  R.  Treat,  Vice  President  Orange 

George  A.  Hopson,  Secretary   Mount  Carmel 

Wm.  L.  Slate,  Jr.,  Treasurer  '. Xew  Haven 

Joseph   W.  Alsop    ' , Avon 

Elijah   Rogers    Southington 

Edward   C.   Schneider    Middletown 

Francis  F.  Lincoln   Cheshire 

STAFF. 
E.  H.  Jenkins,  Ph.D.,  Director  Emeritus. 

Administration.  Wm.   L.   Slate,  Jr.,   B.Sc,  Director  and  Treasurer. 

Miss  L.  M.   Brautlecht,  Bookkeeper  and  Librarian. 
Miss  J.   V.  Berger,  Stenographer  and  Bookkeeper. 
Miss  Mary  E.   Bradley,   Secretary. 
G.  E.  Graham,  In  charge  of  Buildings  and  Grounds. 

Chemistry:  E.  M.  Bailey,  Ph.D.,  Chemist  in  Charge. 

Analytical  C.  E.  Shepard  ~| 

Laboratory.  Owen  L.  Nolan  I    Assistant  Chemists 

Harry  J.  Fisher,  A.B.       {Assistant  Liicmists. 

W.   T.  Mathis  J 

Frank  C.  Sheldon,  Laboratory  Assistant. 
V.  L.  Churchill,  Sampling  Agent. 
Miss  Mabel  Bacon,  Stenographer. 

Biochemical  T.  B.  Osborne,  Ph.D.,  Chemist  in  Charge. 

Laboratory.  H.  B.  Vickery,  Ph.D.,  Biochemist. 

Miss  Helen  C.  Cannon,  B.S.,  Dietitian. 

Botany.  G.  P.  Clinton,  Sc.D.,  Botanist  in  Charge. 

E.  M.   Stoddard,  B.S.,  Pomologist. 
Miss  Florence  A.  McCormick,  Ph.D.,  Pathologist. 
Willis  R.  Hunt,  Ph.D.,  Assistant  in  Botany. 

A.  D.   McDonnell,    General  Assistant. 
Mrs.  W.  W.  Kelsey,  Secretary. 

Entomology.  W.  E.  Britton,  Ph.D.,  Entomologist  in  Charge;    State 

Entomologist. 

B.  H.  Walden,  B.Agr.         \ 

M.  P.  Zappe,  B.S.  >  Assistant  Entomologists. 

Philip  Garman,  Ph.D.       ) 

Roger  B.   Friend,   B.Sc,   Graduate  Assistant. 

John  T.  Ashworth,  Deputy  in  Charge  of  Gipsy  Moth  Work. 

R.   C.   Botsford,  Deputy  in  Charge  of  Mosquito  Elimination. 

Miss  Grace  A.  Foote,  B.A.,  Secretary. 

Forestry.  Walter   O.   Filley,  Forester  in   Charge. 

H.  W.  Hicock,  M.F.,  Assistant  Forester. 
J.  E.  Riley,  Jr.,  M.F.,  In  charge  of  Blister  Rust  Control. 
Miss  Pauline  A.   Merchant,  Stenographer. 

Plant  Breeding.  Donald  F.  Jones,  S.D.,  Geneticist  in  Charge. 

P.   C.  Mangelsdorf,    S.D.,  Assistant   Geneticist. 
H.   R.  Murray,  B.S.,  Graduate  Assistant. 

Soil  Research.  M.  F.  Morgan,  M.S.,  Investigator. 

George  D.   Scarsetii,   B.S.,  Assistant. 

Tobacco  Sub-station  Paul  J.  Anderson,  Ph.D.,  Pathologist  in  Charge. 

at  Windsor.  N.  T.  Nelson,  Ph.D.,  Plant  Physiologist. 

THE    TUTTLE,    MOREHOUSE    &    TAYLOR    COMPANY 


A  Chemical  Investigation  of  Some 
Standard  Spray  Mixtures 

R.  E.  Andrew*  and  Philip  Garman 

Modern  spray  practices  have  become  complicated  procedures. 
The  necessity  of  attaining'  maximum  efficiency  with  a  minimum 
of  labor  has  led  in  the  case  of  fruit  growing  to  the  use  of  high 
powered  outfits  which  apply  spray  mixtures  at  a  rapid  rate  and  to 
the  combination  of  sprays  in  order  to  avoid  separate  applications. 
In  the  combination  of  sprays  there  has  been  much  uncertainty 
of  results  and  failure  to  explain  certain  phenomena  which  have 
not  been  well  understood,  at  least  from  a  chemical  standpoint. 
For  instance,  we  know  that  the  ingredients  of  a  certain  spray 
formula  mixed  in  a  certain  order  give  a  definitely  colored  mixture, 
whereas  an  entirely  different  order  of  combination  may  give  a 
different  appearance.  What  goes  on  under  these  conditions  as 
regards  the  ingredients  themselves  has  only  been  conjectured  by 
the  entomologist,  and  it  is  in  an  attempt  to  throw  some  further 
light  on  what  happens  when  various  insecticides  and  fungicides 
are  put  together  that  the  present  work  was  undertaken. 

Historical  Summary 

Probably  the  earliest  studies  of  spray  mixtures  from  a  chemical 
standpoint  were  made  by  Bradley2  and  Bradley  and  Tartar3, 
who  found  that  there  was  a  distinct  chemical  reaction  between 
lime-sulphur  and  lead  arsenate  resulting  in  the  formation  of 
soluble  arsenic.  The  latter  undesirable  condition  was  found  to 
be  greatly  helped  by  the  addition  of  lime  to  the  mixture. 
Robinson15,  following  this  clue,  described  the  beneficial  action  of 
lime  upon  the  standard  spray  mixture  and  came  to  the  conclusion 
that  lime  prevents  the  reaction  between  lime-sulphur  and  lead 
arsenate  and  does  not  lower  the  polysulphide  sulphur  in  the 
lime-sulphur  to  a  harmful  extent.  Ruth17  made  an  extensive 
investigation  of  spray  mixtures  from  a  chemical  standpoint,  reach- 
ing the  general  conclusion  that  when  these  two  components  are 
mixed,  a  thioarsenate  of  some  kind  is  formed  which  holds  it 
insoluble  in  lime-sulphur  solution,  and  that  thiosulphates  and 
sulphites  are  increased,  possibly  accounting  for  the  improved 
fungicidal  properties  of  the  mixture.  More  recently  Thatcher 
and  Streeter22  have  investigated  the  addition  of  casein,  gelatin, 


*  Until  March,  1926,  Assistant  Chemist  in  the  Analytical  Laboratory. 


49 2  CONNECTICUT    EXPERIMENT    STATION  BULLETIN    278 

nicotine  and  other  preparations  to  the  combined  lead  arsenate, 
lime-sulphur  sprays,  finding  that  casein-lime  and  nicotine  exert 
a  beneficial  action  upon  the  spray  mixture.  Still  more  recently, 
with  the  use  of  somewhat  different  methods,  Goodwin  and 
Martin10  reached  somewhat  different  conclusions,  stating-  that 
casein  and  gelatin  do  not  always  protect  lead  arsenate  from  harm- 
ful reactions  with  lime-sulphur  and  in  fact  give  an  increased 
amount  of  soluble  arsenic,  contrary  to  the  conclusions  of  Thatcher 
and  Streeter.  They  found  furthermore  that  lime  decreased  the 
amount  of  sulphur  in  solution  in  the  spray  mixture,  thereby  reduc- 
ing its  fungicidal  value,  but  that  lime,  if  carbonated,  exerted  little 
or  no  effect  upon  the  mixture. 


Plan  of  Study  and  Methods  Employed 

All  of  the  work  thus  far  described  was  done  with  double  or 
triple  combinations  of  spray  materials  but  the  possible  effect  upon 
the  composition  of  the  mixture  due  to  the  sequence  in  which  the 
separate  ingredients  were  added  was  not  considered.  The  work 
herein  reported  began  with  a  study  of  the  effect  of  different  orders 
of  mixing  upon  the  composition  of  a  mixture  containing  four  ingre- 
dients, but  as  the  work  progressed  it  seemed  advisable  to  extend 
its  scope  to  include  all  possible  double  and  triple  combinations 
as  well. 

In  preparing  the  experimental  mixtures  the  conditions  obtain- 
ing in  practical  spraying  operations  were  followed  as  closely  as 
possible.  Thus,  the  materials  used  were  market  products  of 
standard  grades,  and  the  proportions  in  which  they  were  mixed, 
and  the  method  of  mixing,  are  fairly  representative  of  field 
practice.  It  will  be  seen  that  the  period  of  agitation  was  one 
hour,  which  is  about  the  maximum  time  required  to  apply  a  two 
hundred  gallon  tank  of  spray  mixture,  using  one  gun  or  two  rods. 
With  many  outfits  much  less  time  than  this  would  be  required  so 
that  this  agitation  period  is  probably  nearer  the  maximum  than 
the  minimum  for  the  average  spray  rig. 


FORMULA 

The  complete  formula  used  and  its  equivalent  in  actual  spraying 
practice  are  as  follows  : 

Experimental  Corresponding 

Mixture  Field  Practice 


(1)   Arsenate  of  lead  (acid) 

2.4  grams 

4.0  pounds 

(2)   Nicotine  sulphate 

0.6  cc 

0.96  pint 

(3)    Casein-lime 

0.55  grams 

0.917   pounds 

(4)   Lime-sulphur 

145  cc 

2.6  gallons 

(5)   Water  (distilled),  to  make 

500.0  cc 

100.0  gallons 

CHEMICAL    INVESTIGATION  OF  SPRAY  MIXTURES  493 

PREPARATION    OF   EXPERIMENTAL   MIXTURES 

In  mixing  the  ingredients,  whatever  the  number  chosen,  the 
final  volume  was  brought  to  500  cc  and  the  manipulation  was 
uniformly  as  follows : 

Place  about  485  cc  of  water  in  a  500  cc  graduated  shaking  flask.  Add  the 
ingredients  separately,  in  the  amounts  indicated  by  the  formula,  shaking 
by  hand  for  two  minutes  after  each  addition.  Stopper  the  flask  securely, 
place  in  a  shaking  machine  of  the  revolving  type  and  agitate  the  mixture 
for  one  hour.  Remove  the  flask  from  the  shaking  device  and  allow  the 
mixture  to  stand  for  one  hour.  Filter  on  a  9  cm  filter  paper  using  a 
Buchner  funnel  with  gentle  suction,  transferring  as  much  of  the  insoluble 
material  as  possible  to  the  filter.  Do  not  rinse  the  flask  or  wash  the 
residue  upon  the  filter.  Transfer  the  yellow  filtrate  (A),  to  a  suitable 
flask,  stopper,  and  hold  for  analysis. 

Return  the  filter  ■  with  the  insoluble  residue  to  the  original  graduated 
shaking  flask  and  wash  into  the  flask  also  any  of  the  insoluble  residue 
which  may  have  adhered  to  the  funnel.  Fill  the  flask  to  the  500  cc  mark, 
stopper  securely,  place  in  the  shaking  machine  and  agitate  the  contents 
for  one  hour.  Remove  the  flask  from  the  shaking  device  and  allow  to 
stand  for  one  hour,  after  which  filter  through  a  large  filter.  Do  not  wash 
the  residue.     Reserve  the  filtrate,  solution  (B),  for  analysis. 


EXAMINATION   OF   MIXTURES 

■  The  various  experimental  mixtures  were  examined  with  refer- 
ence to  certain  physical  characteristics  and  to  chemical  composi- 
tion, the  latter  being  confined  to  determinations  of  total  sulphur 
in  the  lime-sulphur  solution  (filtrate  A),  and  of  total  arsenic,  as 
arsenic  pentoxide  (As2Os),  both  in  filtrate  A  and  filtrate  B. 
The  results  obtained  for  total  sulphur  are  of  interest  as  an  index 
to  the  extent  of  chemical  change  which  has  taken  place  in  the 
mixture  so  far,  at  least,  as  the  sulphur  originally  present  has  been 
converted  into  insoluble  forms.  Foliage  injury,  in  part,  results 
from  excessive  amounts  of  soluble  arsenic  in  the  lime-sulphur 
solution ;  and  it  seems  not  improbable  that  the  insoluble  arsenic- 
containing  residue  which  is  deposited  upon  foliage  in  the  process 
of  spraying  might  become,  upon  exposure  to  weather  conditions, 
a  potential  source  of  further  injury.  For  this  reason  the  water- 
soluble  arsenic  in  the  insoluble  residue  was  determined. 


METHODS   OF  ANALYSIS 

The  determination  of  the  small  amounts  of  soluble  arsenic 
involved  in  preparations  made  on  the  scale  of  these  laboratory 
mixtures  presented  some  difficulty.  After  some  preliminary 
trials,  the  method  used  by  Bradley2  and  by  others  whereby  sulphur 
is  oxidized  by  means  of  hydrogen  peroxide  and  arsenic  finally 
titrated  with  dilute  iodine  solution  appeared  to  be  promising.  The 
results,  however,  were  not  satisfactory  and  the  method  is  objec- 


494  CONNECTICUT    EXPERIMENT    STATION  BULLETIN    2/8 

tionable  chiefly  for  the  following  reasons :  it  requires  large 
quantities  of  a  relatively  expensive  reagent  (hydrogen  peroxide)  ; 
the  evaporation  of  a  large  volume  of  liquid  is  time  consuming; 
the  filtration  of  the  large  amount  of  sediment  which  forms  during 
the  evaporation,  and  the  necessary  washing,  introduce  potential 
errors ;  and  finally,  the  iodine  titration  does  not  give  a  sharply 
defined  end  point. 

About  this  time  Cox5  published  a  critical  review  of  certain 
methods  for  the  determination  of  small  quantities  of  arsenic, 
citing  particularly  the  methods  of  Bang  and  Ramberg,  his  expe- 
rience favoring  the  last  named.  As  pointed  out  by  Cox,  neither 
method  involves  any  new  principle,  but,  on  trial,  the  Ramberg 
method  was  found  to  be  adaptable  to  our  problem.  Briefly,  the 
procedure  consists  in  oxidizing  the  sulphur  and  destroying  organic 
matter  by  digestion  with  nitric  and  sulphuric  acids,  removing  the 
excess  of  nitric  acid  by  means  of  ammonium  oxalate,  distilling 
with  hydrochloric  acid  and  titrating  the  arsenic  with  potassium 
bromate  solution,  using  methyl  orange  (i  :  5000)  as  as  indicator. 

The  digestion  was  conducted  in  a  long-neck  Kjeldahl  flask  made 
to  fit  a  condensing  tube  with  a  ground  glass  joint;  thus  the  diges- 
tion and  distillation  were  both  made  without  a  transfer  of  mate- 
rial. Arsenic-free  reagents,  tested  by  means  of  suitable  blanks, 
were  used  throughout.  The  standard  potassium  bromate  solution 
was  prepared  of  such  strength  that  I  cc  was  equivalent  to  0.0005 
gm.  of  arsenic  pentoxide  (As2Os). 

The  procedure  in  detail  as  used  by  us  is  as  follows : 

Arsenic  in  lime-sulphur  solution  (Solution  A).  Transfer  100  cc  of  the 
solution  to  the  digestion-distillation  flask,  add  a  few  glass  beads,  50  cc  of 
concentrated  nitric  acid  and  evaporate  over  a  low  flame  until  the  volume 
is  reduced  to  about  25  cc.  Cool,  add  25  cc  of  concentrated  sulphuric  acid 
and  heat  until  fumes  of  sulphuric  acid  appear.  From  a  suitable  dropping 
device  add  50  cc  of  concentrated  nitric  acid  dropwise,  meanwhile  boiling 
the  solution  very  gently.  Continue  the  boiling  until  sulphuric  acid  fumes 
appear.  Cool,  add  25  cc  of  saturated  ammonium  oxalate  solution  and  again 
boil  until  fumes  of  sulphuric  acid  are  noticed.  Cool,  rinse  the  neck  of  the 
flask  with  20  cc  of  water  and  then  add  2  grams  of  ferrous  sulphate,  50  cc 
of  concentrated  hydrochloric  acid  and  0.1  gram  of  potassium  bromide. 
(If  any  yellow  or  brown  color  appears  at  this  point  nitrogen  acids  are 
present  and  the  experiment  must  be  rejected.)  Connect  the  flask  with  the 
condensing  tube,  adjust  a  receiving  flask  containing  150  cc  of  water,  and 
allow  the  condenser  to  dip  about  1  cm.  below  the  surface  of  the  liquid 
therein.  Distill  at  such  a  rate  that  20  to  25  cc  of  distillate  are  obtained 
in  about  10  minutes.  Heat  the  distillate  to  500  C,  add  three  drops  of 
methyl  orange  and  titrate  at  once  with  standard  potassium  bromate  solu- 
tion, adding  this  reagent  very  slowly  as  the  end  point  is  approached.  The 
end  point  is  reached  when  the  red  color  of  the  indicator  is  discharged. 
Each  cc  of  potassium  bromate  used  corresponds  to  0.0005  gram  of  As^Oo. 

Arsenic  in  Solution  B.  Transfer  50  cc  of  the  solution  to  the  digestion- 
distillation  flask,  add  50  cc  of  concentrated  nitric  acid  and  evaporate  over 
a  low  flame  until  the  volume  is  reduced  to  about  25  cc.  Cool,  add  25  cc  of 
concentrated  sulphuric  acid  and  boil  until  sulphuric  acid   fumes   appear. 


.    CHEMICAL    INVESTIGATION  OF  SPRAY  MIXTURES  495 

Cool,  add  10  cc  of  concentrated  nitric  acid  and  again  heat  until  fumes  of 
sulphuric  acid  are  noted.  Cool,  add  25  cc  of  saturated  ammonium  oxalate 
solution  and  from  this  point  proceed  as  directed  in  the  previous  paragraph. 

Total  sulphur  in  Solution  A.  Total  sulphur  was  determined  substan- 
tially according  to  the  official  procedure1  except  that  oxidation  of  sulphur 
was  effected  by  means  of  hydrogen  peroxide  in  alkaline  solution  as  allowed 
by  a  former  optional  method.13 

Transfer  10  cc  of  solution  A  to  a  250  cc  beaker  containing  10  cc  of  a 
10  per  cent  solution  of  sodium  hydroxide,  50  cc  of  water  and  50  cc  of 
hydrogen  peroxide.  Cover  the  beaker  with  a  watch  glass  and  heat  for 
one  hour  on  a  steam  bath.  Cool,  acidify  with  dilute  hydrochloric  acid 
(1  to  1),  and  precipitate  the  sulphur  as  barium  sulphate.  Calculate  the 
percentage  of  sulphur  from  the  weight  of  barium  sulphate,  using  the  factor 
0.1374. 

PRELIMINARY  EXPERIMENTS 

The  adaptability  of  the  method  for  the  determination  of  arsenic 
as  described  may  be  illustrated  by  the  following  experiments. 
Blanks  on  the  reagents,  in  the  amounts  used  in  the  method, 
showed  titerable  substances  equivalent  to  0.3  cc  of  standard 
potassium  bromate  and  this  correction  was  uniformly  made  in  all 
determinations. 

, Arsenic,  as  As205 ^ 

Present           Added  Total  Recovered 

Material                                      gm.                 gm.  gm.  gm. 

100  cc  water -\-i  gm.  sugar     0.01160  0.01160  0.01160 

100  cc  water -j- 1  gm.  sugar     0.01160  0.01160  0.01160 

Lime-sulphur-Lead  arsenate   0.00613        0.01160  0.01773  0.01775 

0.01160  O.01773  0.01773 


INTERPRETATION    OF    RESULTS 

In  the  analytical  data  herein  reported  total  sulphur  is  expressed 
in  terms  of  grams  per  100  cc  of  the  lime-sulphur  solution. 
x\rsenic  is  expressed  in  percentages  of  As2Os  based  on  the  amount 
of  lead  arsenate,  2.4  grams,  present  in  the  mixture. 

In  the  tables  also  abbreviations  are  necessary  and  the  following 
are  used:  L.A.  =  Lead  arsenate;  L.S.  —  Lime-sulphur;  N.  S.  = 
Nicotine  sulphate ;  C.L.  =  Casein-Lime ;  L.  =  Lime ;  Blk.  = 
Black ;    G.  =  Grey ;    G.B.  =  Greyish-black. 


496 


CONNECTICUT    EXPERIMENT    STATION 


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498  connecticut  experiment  station  bulletin  2/8 

Discussion 

Effect  of  Adding  Lime-Sulphur  to  Different  Ingredients 
Separately  and  Combined  (Tables  i  to  3) 

It  will  be  seen  that  addition  of  lime-sulphur  to  lead  arsenate 
brings  about  a  tremendous  increase  in  soluble  arsenic, — nearly  136 
times  the  original  content  of  the  lead  arsenate  alone.  When 
lime-sulphur  is  added  to  nicotine  sulphate  and  lead  arsenate  in 
combination  there  is  likewise  a  great  increase, — 34  to  140  times, 
while  in  the  complete  quadruple  combination  the  increase  is  not 
so  great,  due  probably  to  addition  of  casein-lime  in  the  mixture. 
It  is  thus  evident  that  there  is  an  important  reaction  between  lime- 
sulphur  and  lead  arsenate,  but  that  this  is  not  increased  by  nicotine 
sulphate,  and  is  lessened  when  casein-lime  is  added. 


CHEMICAL    INVESTIGATION  OF  SPRAY  MIXTURES 


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chemical  investigation  of  spray  mixtures  50i 

Effect  of  Adding  Nicotine  Sulphate  to  Different 
Ingredients  Separately  and  Combined 

(Tables  4  to  8) 

A  study  of  Tables  4  to  8  shows  that  there  is  a  negligible  action 
when  nicotine  sulphate  and  lime-sulphur  are  mixed  together  as 
regards  total  sulphur  in  solution.  There  is  likewise  little  or  no 
action  when  nicotine  sulphate  and  lead  arsenate  are  mixed 
together.  When  nicotine  sulphate  is  added  to  lime-sulphur  and 
casein-lime  in  combination,  not  so  much  sulphur  is  precipitated 
from  the  solution  although  the  difference  is  small  and  of  doubtful 
importance.  When  added  to  lead  arsenate  and  casein-lime  there 
is  a  distinct  increase  in  soluble  arsenic  and  when  nicotine  sulphate 
is  added  to  lead  arsenate  and  lime-sulphur  in  combination  there  is 
a  decrease  in  soluble  arsenic,  and  also  a  decrease  in  the  amount  of 
sulphur  in  solution.  Added  to  triple  combinations  as  in  Table  8, 
there  are  variable  results.  The  sulphur  content  of  the  filtrate  is 
only  slightly  altered  and  the  soluble  arsenic  is  decreased  in  8  cases 
but  increased  in  4. 


5°2 


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504  connecticut  experiment  station  bulletin  278 

Effect  of  Adding  Casein-Lime  to  Different 
Ingredients  Separately  and  Combined 

(Tables  9  to  13) 

It  will  be  seen  from  Table  9  that  the  addition  of  casein-lime 
increased  the  soluble  arsenic  and  reduced  the  sulphur  when  mixed 
with  lead  arsenate  and  lime-sulphur  alone.  When  added  to  lead 
arsenate  and  lime-sulphur  in  combination,  the  amount  of  soluble 
arsenic  is  greatly  reduced  and  the  sulphur  in  solution  is  increased. 

When  added  to  nicotine  sulphate  and  lead  arsenate  in  combina- 
tion the  soluble  arsenic  is  distinctly  increased,  but  when  added 
to  lime-sulphur  and  nicotine  sulphate  the  sulphur  content  of  the 
solution  is  not  greatly  altered.  In  quadruple  mixtures,  Table  13, 
there  seems  to  be,  in  general,  an  increase  of  sulphur  in  solution 
where  casein-lime  is  used  over  mixtures  where  this  material  is 
omitted;  and,  in  general,  the  soluble  arsenic  is  reduced,  but  it 
may  sometimes  be  increased. 

Effect  of  Replacing  Casein-Lime  with  ■ 
Pure  Lime  (Table  14) 

In  order  to  find  out  whether  the  casein  or  lime  of  the  casein- 
lime  mixture  was  responsible  for  the  results  noted  in  Tables  9  to 
13,  a  quantity  of  pure  lime  (CaO),  equivalent  to  the  amount  used 
in  the  casein-lime,  was  substituted  (Di).  This  amount  was  then 
doubled  (D2).  It  will  be  seen  that  the  amount  of  soluble  arsenic 
is  decreased  as  much  or  more  by  lime  alone  as  by  casein-lime 
(Exp.  No.  2)  ;  also  that  the  amount  of  sulphur  in  solution  is 
not  greatly  reduced  by  the  additional  lime. 

Effect  of  Different  Orders  of  Mixing  on 
Quadruple  Mixtures  (Table  15) 

It  is  easily  demonstrated  that  different  orders  of  mixing  pro- 
duce differently  colored  mixtures,  but  to  determine  if  possible  the 
value  of  this  criterion  for  judging  spray  mixtures  Table  15  was 
prepared.  It  will  be  seen  that  some  of  the  mixtures  are  dark  in 
color  while  others  are  light.  It  was  noted  in  the  course  of  the 
work  that  some  of  the  blackness  of  the  resulting  spray  was  due 
to  the  mixture  of  lime-sulphur  and  nicotine  sulphate  as  well  as 
the  formation  of  lead  sulphide  as  noted  by  others.  The  actual 
color  of  the  sediment  does  not  vary  greatly,  but  there  is  a  con- 
siderable variation  in  the  turbidity  of  the  filtrate,  certain  ones 
remaining  clear,  while  others  produce  a  decided  murkiness.  The 
turbid  filtrates  were  tested  by  chemical  means  and  found  to  be 
due  to  a  very  finely  divided  sulphur  and  not  to  lead,  calcium  or 


CHEMICAL    INVESTIGATION  OF  SPRAY  MIXTURES 


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506  CONNECTICUT    EXPERIMENT    STATION  BULLETIN    2"/8 

nicotine.  This  fact  is  of  some  significance  in  spraying"  practices 
since  it  has  been  demonstrated  that  colloidal  sulphurs  are  impor- 
tant fungicides.28  Whether  such  combinations  as  these,  however,, 
contain  enough  colloidal  sulphur  to  affect  the  efficiency  of  the 
spray  has  not  been  determined. 

It  will  be  noted  that  combinations  showing'  the  lowest  arsenic 
in  solution  (Nos.  5  and  12)  are  both  extremely  low  in  soluble 
sulphur  and  that  both  filtrates  are  clear.  It  would  probably  not  be 
wise  to  select  merely  on  the  basis  of  soluble  arsenic  and  sulphur 
content  alone,  although  Ave  know  from  the  work  of  Saffro19  that 
spray  injury  may  be  caused  by  calcium  poly  sulphides  and  to  a  less 
extent  by  calcium  thiosulphate  (p.  32).  An  attempt  to  avoid  spray 
injury  would,  therefore,  include  selection  of  mixtures  low  in 
sulphur  and  arsenic  in  solution,  but  these  would  probably  be 
reduced  in  fungicidal  action  since  the  filtrates  are  clear  and  the 
total  sulphur,  supposedly  the  active  forms,  is  reduced  25%  or 
more  (Nos.  5  and  12).  It  is  important  to  note  that  in  all  cases 
the  greater  part  of  the  soluble  arsenic  is  found  in  the  residue 
which  emphasizes  the  necessity  of  cleaning  the  spray  tank  fre- 
quently, in  order  to  avoid  accumulation  of  sludge  from  previous 
tanks,  and  the  importance  of  ample  agitation  to  avoid  this 
difficulty. 

General  Conclusions 

(1)  The   Bramberg   method   of    determining   small   amounts   of 

arsenic  has  been  found  adaptable  to  the  determination  of 
soluble  arsenic  in  spray  mixtures. 

(2)  Lime-sulphur  reacts  strongly  with  lead  arsenate*  giving  in- 

creased soluble  arsenic  and  decreased  sulphur  in  solution. 
It  reacts  similarly  with  lead  arsenate  and  nicotine  sulphate 
in  combination  and  with  lead  arsenate  and  casein-lime  but 
the  reaction  is  not  as  great  in  the  latter  case. 

(3)  Nicotine  sulphate  does  not  react  with  lead  arsenate  or  with 

lime-sulphur  so  far  as  indicated  by  the  chemical  data ;  a 
color  change  is  noted,  the  significance  of  which  is  not 
explained.  When  added  to  lead  arsenate  and  casein-lime 
together  the  soluble  arsenic  is  increased ;  added  to  lead 
arsenate  and  lime-sulphur  together  there  is  a  marked 
decrease  in  soluble  arsenic  and  also  a  decrease  in  the 
amount  of  sulphur  in  solution.  When  added  to  triple 
combinations  of  lead  arsenate,  casein-lime  and  lime-sul- 
phur, variable  results  are  noted. 

(4)  Casein-lime   increases   the    soluble   arsenic    content    of    lead 

arsenate  when  mixed  with  it  alone.     When   mixed  with 


*  Acid  lead  arsenate  is  implied  wherever  lead  arsenate  is  mentioned. 


CHEMICAL    INVESTIGATION  OF  SPRAY   MIXTURES  507 

lime-sulphur  alone  the  amount  of  sulphur  in  solution  is 
somewhat  reduced.  When  added  to  nicotine  sulphate  and 
lead  arsenate  the  soluble  arsenic  is  distinctly  increased,  but 
when  added  to  lime-sulphur  and  nicotine  sulphate  the  sul- 
phur content  of  the  solution  is  not  greatly  altered.  In 
quadruple  mixtures  there  is,  in  general,  an  increase  of  sul- 
phur in  solution  due  to  the  casein-lime  and  there  is  in 
general  a  decrease  in  soluble  arsenic.  The  latter,  however, 
may  sometimes  be  increased. 

(5)  The  lime  in  casein-lime  is  largely  responsible  for  the  decrease 

in  soluble  arsenic  where  this  material  is  used. 

(6)  Different  orders  of  mixing  quadruple  mixtures  give  different 

results,  but  so  many  factors  are  involved  and  the  varia- 
tions are  so  small  that  the  selection  of  improved  mixtures 
seems  an  impossibility. 

(7)  Colloidal  sulphur  is  sometimes  formed  in  the  spray  mixtures. 

(8)  The  color  of  the  resulting  mixture  is  not  a  satisfactory  means 

of  judging  a  spray  solution. 

Bibliography 

1.  Association  of  Official  Agricultural   Chemists,  Methods   of  Analysis, 

1924. 

2.  Bradley,  C.  E.     Soluble  arsenic  in  mixtures  of  lead  arsenate  and  lime- 

sulphur  solution.  In  Journal  of  Industrial  Engineering  Chemistry 
1 :   606-607 :    1009. 

3.  Bradley,  C.  E.,  and  Tartar,  H.  V.     Further  studies  of  the  reaction  of 

lime-sulphur  solution  and  alkali  waters  on  lead  arsenates.  In 
Journal  of  Industrial  Engineering  Chemistry  2:    328-329:    1910. 

4.  Cook,  F.  C,  and  Mclndoo,  N.  E.     Chemical,  physical  and  insecticidal 

properties  of  arsenicals.  U.  S.  Department  of  Agriculture,  Depart- 
ment Bulletin  No.  1147,  1923. 

5.  Cox,  H.  E.     In  the  Analyst,  50:    586:    3,  1924. 

6.  De  Ong,  E.  R.     California  University  Agricultural  Experiment   Sta- 

tion Bulletin  338:  1921.  Survey  of  waters  made  in  1919  and 
found  that  many  had  a  high  chlorine  content.  Concluded  that 
basic  lead  arsenate  should  be  used. 

7.  Ellett,  W.  B.,  and  Grisson,  J.  T.     The  amount  of  arsenic  in  solution 

when  lead  arsenate  is  added  to  different  spray  solutions.  Virginia 
Experiment  Station  Technical  Bulletin  8:    160-164:    1915. 

8.  Fulmer,   H.   L.,   and   Caesar,    Lawson.     Lime-sulphur    wash,    Ontario 

Agricultural  College,  Bulletin  177:    1909. 

9.  Fields,  W.  S.,  and  Elliott,  J.  A.     Making  bordeaux  mixture  and  some 

other  spraying  problems.  Arkansas  Agricultural  Experiment 
Station,  Bulletin  172:    33:    1020. 

10.  Goodwin,  W.,  and  Martin,  H.    In  Journal  of  Agricultural  Science  15: 

307,  476-490:    1925- 

11.  Haywood,  J.  K.     U.  S.  Department  of  Agriculture,  Bureau  of  Chem- 

istry, Bulletin  101.  States  that  increase  in  fungicidal  action  of 
mixture  is  due  to  formation  of  thiosulphate  which  later  changes 
to  sulphites. 

12.  Harcourt,  R.     Lime-sulphur  wash.     In  annual  report,  Ontario  Agri- 

cultural College  and  Experiment  Farm  36:    100-102:    1910. 

13.  Journal  Association  of  Official  Agricultural  Chemists,  1 :    75,:    1915. 


508  CONNECTICUT    EXPERIMENT    STATION  BULLETIN    2/8 

14.  McDonnell,  C.  C,  and  Graham,  J.  J.  T.     The  decomposition  of  dilead 

arsenate  in  water.  In  Journal  American  Chemical  Society  29: 
1912-1918:    1917. 

15.  Robinson,  R.  H.     Beneficial  action  of  lime  in  lime-sulphur  and  lead 

arsenate  combination  spray.  In  Journal  Economic  Entomology 
12:    420-433:    I9I9- 

16.  Robinson,  R.  H.     The  valuation  of  commercial  arsenate  of  lead.     In 

Journal  Industrial  Engineering  7:    409-502:    1915. 

17.  Ruth,   W.  E.     In  Illinois   Horticultural   Transactions,   new   series   49; 

393:    I9I5- 

18.  Ruth,    \Y.    E.     Chemical    studies    of    the    lime-sulphur    lead    arsenate 

spray  mixture,  Iowa  Agricultural  Experiment  Station  Research 
Bulletin  12:    409-419:    1913. 

19.  Saffro,  V.  I.     An  investigation  of  lime-sulphur  injury;    its  causes  and 

prevention.  Oregon  Agricultural  College  Experiment  Station, 
Research  Bulletin  No.  2,  1913.  Page  32.  Lime-sulphur  injury  is 
caused  by  the  calcium  polysulphides  and  to  a  less  extent  by 
calcium  thiosulphate.  Advised  increased  dilution.  Increased  boil- 
ing of  the  lime-sulphur  affects  burn.  Density  or  specific  gravity 
not  a  good  index  of  its  value. 

20.  Sanders,  G.  E.,  and  Brittain,  W.  H.     The  toxic  value  of  some  poisons 

alone   and   in   combination   with    fungicides   on   a   few   species  of 

biting  insects.  In  Proceedings  of  the  Entomological  Society  of 
Nova  Scotia  for  1916,  No.  2 :  55-64. 

21.  Smith,   C.   R.     The   determination   of  •arsenic.     U.    S.   Department  of 

Agriculture,  Bureau  of  Chemistry,  Circular   102:   1912. 

22.  Thatcher,    R.    W.,    and    Streeter,   Leon    R.     Chemical    studies    of    the 

combined  lead  arsenate  and  lime-sulphur  spray.  New  York  State 
(Geneva)  Agricultural  Experiment  Station  Bulletin  521  :    1924. 

23.  Van  Slyke,  L.  L,  Hedges,  C.  G,  Bosworth,  A.  W.     A  chemical  study 

of  the  lime-sulphur  wash.  New  York  State  (Geneva)  Agricul- 
tural Experiment  Station  Bulletin  319:  410-411:  1909.  Page 
384,  Effect  of  addition  of  lime-sulphur  in  sulphide  sulphur  form 
decreased,  thiosulphate  increased. 

24.  Vermorel,  V.,  and  Dantony,  E.     Composition   chimique  des  Bouillies 

sulfo-calciques  employees  contre  les  Insectes  et  les  Maladies  des 

Plantes.  Villefranche  (Rhone)  Librairie  Agricole  du  ''Progres 
agricole  et  viticole"  1919. 

25.  Wallace,  Errett.     Spray  injury  induced  by  lime-sulphur  preparations. 

Cornell  Agricultural  Experiment  Station,  Bulletin  288;  1910. 
Page  107,  "The  active  agent  in  causing  lime  sulphur  injury  is 
doubtless  the  soluble  sulphur  in  the  form  of  a  calcium  sulfid  and 
is  applied  as  such." 

26.  Wilson,   H.   F.     Combination   sprays  and  recent  insecticide   investiga- 

tions. In  Proceedings  Entomological  Society  British  Columbia 
No.  3,  n.s.  9-16:    1913. 

27.  Wilson,   H.   F.     Insecticide   Investigations   of   1914,   in   Biennial   Crop 

Pest  and  Horticultural  Report  for  1913  and  1914-  Oregon  Agri- 
cultural Experiment  Station,  page  137. 

28.  Young,  H.  C.     Crop  Protection  Digest  No.  3.  403-435 )    1923- 


Grateful  acknowledgment  is  made  to  Dr.  E.  M.  Bailey  who  has  given 
much  aid  both  in  the  preparation  of  the  manuscript  and  by  criticism  and 
suggestions  as  the  work  progressed.  The  authors  also  wish  to  thank 
Dr.  W.  E.  Britton  for  advice  and  criticism  during  the  course  of  the 
investigation. 


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